Refractory heat exchanger



1955 K. w. STOOKEY 3,220,713

REFRACTORY HEAT EXCHANGER Filed Aug. 9, 1962 3 Sheets-Sheet 1 INVENTOR. KENNETH W. STOOKEY BY (mm-1;. Mum

ATTO R N EY Fig] Nov. 30, 1965 w. STOOKEY 3, 20,713 REFRACTORY HEAT EXCHANGER Filed Aug. 9, 1962 3 Sheets-Sheet 2 INVENTOR. KENNETH W. STOOKEY ATTORNEY Nov. 30, 1965 K. w. STOOKEY I 3,220,713 v REFRACTORY HEAT EXCHANGER Filed Aug. 9, 1962 3 Sheets-Sheet s 72 INVENTOR. KENNETH W. STOOKEY BY FIG-4 mg. m

ATTO NEY United States Patent 3,220,713 REFRACTORY HEAT EXQHANGER Kenneth W. Smokey, 211 Lee St., Markle, ind. Filed Aug. 9, 1952, Ser. No, 215,846 23 Claims. (Cl. 263-213) This invention relates to a refractory heat exchanger of the kind referred to and claimed in my co-pending application, Serial No. 119,893, filed June 27, 1961, now US. Patent No. 3,129,931.

It has been known in the art to use metal and metal alloy heat exchanger or recuperator constructions, but in general such constructions are inherently limited by the composition of the material of construction because they are incapable of sustaining the high temperatures which are sometimes required for proper operation. Seldom do designers of heat exchangers or recuperators having metal or metal alloy structures recommend a preheat in excess of 1000 F. because of the tendency of the metal or alloy to deteriorate at higher temperatures. Nevertheless, these metal or alloy materials of construction are useful because of the high pressures which may be employed with such heat exchangers. In an effort to increase the heat resistivity of the heat exchanger or recuperator, some efforts have been made to replace the metal or alloy composition with a more refractory material, such as ceramic components or the like. These efforts have largely been unsuccessful because of the inability of the ceramic refractory components to maintain a suitable seal because of their tendency to fracture when exposed to temperature differential or to return to their original position when cooled. As a result, neither the metal, metal alloy nor ceramic refractory material of construction have proved adequate for a combination of high temperature and high pressure heat exchange operation.

One of the advantages of a highly efl icient heat exchanger or recuperator operation is that the preheated air is more eificient in increasing the flame temperature and flame speed to improve burner operation and to save fuel. For these reasons, a heat exchanger or recuperator operation offers numerous advantages in the efficient combustion of fuel wherein more heat can be released in a unit volume of space allowing a furnace to be made smaller, or to turn out a greater volume of work from a given size furnace. With higher preheats it is also possible to utilize more or different kinds of fuels with variable calorific content. For example, all fuel will produce higher flame temperatures with a high preheat and high pressure air supply.

Accordingly, it is one of the main objects of the present invention to provide an improved heat exchanger or recuperator construction having a heat resistant refractory ceramic composition and in which the refractory components, being inherently more heat resistant than metal or metal alloys, allow for higher temperature of operation.

One of the important features of the present invention is that the refractory heat resistant material of construction is provided in the form of components which maintain a sealed condition of the heat exchanger or recuperator and will not develop leakage paths during operation which interfere with the efficiency of operation of the heat exchanger. Moreover, the sealed relationship of the refractory components is maintained during the heat exchange operation by means of novel floating construction which permits the ceramic components to move one relatively to the other without injuring or damaging the internal seal.

In accordance with the present invention, there is provided a heat exchanger using highly conductive refrac- 3,220,713 Patented Nov. 30, 1965 ice tori-es such as silicon carbide tubes or the like which serve as the heat conductive medium between the two fluids being heat exchanged.

It is one of the objects of the present invention to provide a refractory ceramic composition heat exchanger that is usable at substantial pressure differentials which will maintain such pressure differentials Without substantial loss during operation.

It is a further object of the invention to provide a refractory ceramic composition heat exchanger or recuperator in which the components are floatably related and can adjust during various temperature differentials both horizontally and vertically in order to maintain a proper sealed relation of the parts of the heat exchanger.

A still further object of the present invention is to provide a single pass heat exchange between two fluids which ing sealed components which can move relatively to.

each other to maintain the sealed relation of each conduit end with its associating chamber.

A further object of the present invention is to improve the heat exchange efficiency of the system by providing a novel core construction wherein the hot gas flow is produced whereby the heat absorptive and heat radiation surfaces are increased, both of these factors thereby improving the heat exchange operation.

A further feature of the present invention is to provide a novel floating joint between ceramic components of the heat exchanger or recuperator which, being resilient, allows floating movement between contiguous ceramic components. The natural resiliency of the joint together with a novel tapered construction insures both relative movement and completeness of seal regardless of the degree of relative movement which occurs responsively to temperature change.

It is a further object of the invention to provide a heat exchanger or recuperator construction having a novel arrangement of chambers and heat exchange conduits in which the flow of gases can be directed either in concur-- rent or counter current heat exchange flow and there-- fore depending upon the temperature desired, the flow of gases can be accordingly directed.

A still further object of the invention is to provide a novel ceramic sleeve construction having an integral portion which defines an annular heat exchange passage for one of the gaseous flow medium.

One of the important features of the present invention is the usage of refractory components which define two conduits having gaseous media therein flowing in heat exchange relation, the inner of said conduits including a core which improves the heat absorptive and heat reflective capacity of the conduit, said conduits and core being relatively movable both longitudinally and laterally in order to maintain the sealed relation of the heat exchange components despite temperature differentials so that the two gaseous media are unmixed.

Other objects and features of the present invention will become apparent from a consideration of the following detailed description of the invention wherein a plurality of embodiments are selected by way of example, and wherein:

FIGURE 1 is a sectional view taken through the center of a heat exchanger and indicating by wavy-line arrows and smooth-line arrows the counter current flow of hot gas and inlet air to be preheated, respectively;

FIGURE 2 is a sectional view taken on line 22 of FIGURE 1;

FIGURE 3 is an isometric detail view of one of the ceramic blocks forming a support for the conduit and constituting part of the header wall; and

FIGURE 4 is a sectional view of a second embodiment of my invention and showing a heat exchanger with concurrent flow of the gaseous media.

Referring now to the drawings, FIGURES 1-3 show a counter flow arrangement wherein hot flue gases from the heating unit (not shown) are introduced to the heat exchanger or recuperator through an inlet 12 to a hot air header inlet chamber 14. The heat exchanger is provided with a conventional fire brick lining 11 enclosed by a steel shell housing 13 having insulation 15 disposed therebetween. The housing may assume any particular shape, such as rectangular or circular. An inspection hole, or peep site 17 is disposed in the upper housing so that the top terminal wall 28 can be inspected. The roof 19, having an outside insulation 21, may be arched or flat shaped. The hot flue gases follow generally the direction of the wavy-line arrows and after entering chamber 14, they are directed downwardly through a number of passages 16, defined by counterweight ceramic blocks 18 and a top terminal head block 20. The hot flue gases after having circulated through the heat exchanger or recuperator 10 are collected in outlet chamber 50 and led to a stack (not shown) which is vented to atmosphere. The incoming gas, which is generally air, and is heated by the flue gases, enters an inlet 22 and flowing countercurrently to the hot flue gases acquires a substantial por tion of its heat and then exits through an opening 24 in portal 27 where it is then conducted in its heated condition to the heating units and is used for burning fuel or other purposes.

The general construction shows a middle chamber 26 having top and bottom movable or fioatable walls 28 and 30 respectively, each of which is constructed of a plurality of head blocks 20. It is characteristic of these upper and lower walls 28, 30 that they can float or move by reason of the separate expansion and contraction of its constituent head blocks 20. Each head block in the upper and lower wall is separated from its contiguous head block by a floating joint using a highly refractory alumina-silica fiber, sold under the trade name FIBER- FRAX which is available through the Refractory Division of Carborundum Company. The FIBERFRAX has a melting temperature inexcess of 3200 F. and is of particular value since it retains a natural resilience at temperatures somewhat exceeding 2300 F. The FI- BERFRAX is located within a rabbet-forming channel 29 around the periphery of each head block to hold the gasket 32 of FIBERFRAX rope, bulk fiber and plastic which is compacted to a predetermined density and depth within the channel. The gasket is tapered in cross section and owing to the resiliency of the material is under different degree of compaction along its length because of this tapered cross section. For this reason, the seal between each head block is maintained regardless of the temperature of variation to which the head block is subjected. The gasket 32 permits, therefore, a floating action of each constituent head block thereby precluding a communication of thermal stress from one head block to another. Thermal stress and distortion stresses which are generated in the recuperator are non-cumulative during heating and cooling within the heat exchanger. Heretofore, when a ceramic composition heat exchanger was heated up or cooled down, the dimensional changes which occurred would produce fracturing of the ceramic components because of the inherent inelasticity of this material under stress if not properly countered by proper design. The ceramic head blocks are of clay or other refractory materials having sufficiently great heat resistance, and each is separated from its contiguous block by the special ceramic gasket 32 which is about Ms inch in dimension. The lower head wall 30 is supported on a number of piers 34, one located at each of the four corners of each head block. As shown in FIGURE 3,

a pier is large enough to support four intersecting corner portions of four of the head blocks.

Extending between the upper and lower head walls are a number of conduits 36 of silicon carbide composition or the like. The ends of the conduits 36 are tapered or may be ball and socket and fit within complementary tapered seats 38 of the associate head block 20 (FIGURE 1) and are maintained in sealing relation therewith by the weight of blocks 18 which urge head block 20 into sealing engagement with the conduit 36. The hot flue gas is thus caused to describe a downward movement within the conduit 36 in the direction of the wavy-line arrows which are shown internally of the conduit. The conduits are capable of sustaining temperatures as high as 2500-2600 F. The material, comprised of silicon carbide, has a high thermal conductivity, approximately ten times that of fire clay or other similar refractories, which makes it suitable as a heat exchange barrier. The conduit combines a high refractiveness with a low permeability and has considerable strength at high operating temperatures to make it resistant to rupturing or crushing. Moreover, the material has a high resistance to spalling, flame abrasion and chemical attacks from combustion products of commercial fuels, all of the temperature of usage, i.e., 250()2600 F. For certain chemical gases that might be heated instead of air which might be corrosive or which might attack silicon carbide, the heat exchanging tubes may be made from a chemical resistant refractory, but at a loss of heat conductivity through the walls. Within each conduit 36 is a stack of core material components 42 (FIGURE 2) which constitute radiation inserts which, for purposes of illustration only, are cross shaped. The inserts may, of course, assume any of several different shapes so long as the main purpose of serving as heat exchanging media is served. The inserts 42 serve the function of increasing the heat absorptive surfaces receiving heat from the hot gases as they pass longitudinally through the conduit 36. For example, in a 7-inch I.D. conduit there has been used with satisfactory results a cross shaped insert having a width in the order of 6% inches times 6% inches, about inch thick and made up in 6-12 inch lengths. This adds about 2.25 square feet of additional heat absorbing surface per foot of conduit length since all exposed areas are active areas. The surface of the conduit per foot of length is 1.83 square feet which makes a total of 4.08 square feet, or an increase of 123% heat receiving surface. The inserts are not an integral part of the conduit but are free to move relatively to the conduit and also relatively to each other. The material is preferably of refractory or metallic alloy material, whichever is cheaper, and is selected on the basis of its emissivity and is capable of lasting during the entire wear life of the heat exchanger or recuperator without requiring service. The inserts are formed in a stack lying end to end, and the entire stack is supported from the lowermost insert (FIGURE 1) through an integral flange portion 44 of lower head block 20.

Although the increase of heat made available at the outer surface of conduit 36 is not in direct relationship to the increase in surface due to a required secondary transfer of heat from the inserts to the conduit wall 36, the usage of the inserts will, when the heat exchanger is operating at high temperatures, produce on the order of -85% increase of heat made available at the outer surface of the conduit 36.

As the hot flue gases flow through the conduits 36, the surfaces of the inserts 42 will pick up heat in the same way that it is picked up by the walls of the conduits. Then as the conduit Walls lose heat at their outer surface, there will be a temperature drop creating a temperature differential between the interior walls of the conduits and the inserts 42 received therein. Such differential will cause heat to flow from the insert to the conduit as a function of solid-solid radiation. At the high temperaassent tures in which the heat exchanger will normally operate, this is a most eificient method of heat transfer since even a small differential of temperature causes the transfer of vast amounts of energy. With the application of the radiation inserts, it is possible to make efficient use of the heat exchanger conduits, and it becomes possible to pick up and transmit heat through the silicon carbide composition walls of the conduits up to the limit of the thermal stresses they can endure. From the cross-sectional shape of the insert 42 (FIGURE 2), it will be seen that they offer no resistance to longitudinal movement of the flue gases through the length of the conduits, and, therefore, substantially no pressure drop is caused during the flow of gases from chamber 14 to chamber 59 where the cold fiue gases then exit through opening 52 to the stack (not shown) where they are vented to atmosphere.

Surrounding each conduit 36 is a stack of convection sleeve assemblies 54 which may be of refractory material, and each includes a small rib 58 (FIGURE 2) at 90 spaced intervals around the cross-sectional circumference of the sleeve to provide a spacing between the sleeve 54 and conduit 36 which is of relatively narrow annular cross section. Referring to FIGURE 1, the annular space 60 connects with the air header chamber 62 having an air inlet 22 and an air flow, indicated by smooth-line arrows, is directed from the inlet 22 into the header 62, and a continuous passage of air travels upwardly within the annular cross section passage 60 defined by the stack of sleeves 54 and passing countercurrently to the flow of hot gas within the conduit 36 becomes heated and is discharged at the upper end of the stack of sleeves and enters chamber 26 where it is then collected and leaves the heat exchanger or recuperator through opening 24. The use of the convection sleeves controls the flow path and mass velocity of the air and increases the total effective heat exchange surface by which the air receives heat from the internal surfaces of the annular chamber 60. This increase in potential efiiciency allows a relative reduction in the size of the heat exchanger. The relative absorption of heat from the surfaces is about 45% from the internal surface of the sleeve and 55% from the external surface of the conduit 36. Since the air is a diatomic material and will neither receive nor give up heat by radiation, it must be heated or cooled by convection only, and the only way to increase the heat pickup by the air is to find a way of increasing the heat absorption internally of the conduit 36 which in turn will be reflected by conduction to the air flow between the convection sleeves 54 and conduit 36. In contrast with the mechanism in which the air receives its heat, the heat internally of the conduit 36 is abstracted from the clear gases of combustion by radiation of these gases to the radiation inserts and internal conduit wall. Therefore, the mechanics of heat exchange internally of the conduit 36 and externally of the conduit 36 is by distinctly different mechanisms, but the present invention employs a unique system for most efficiently abstracting heat by each of these distinct mechanisms, abstracting it on the one hand from the combustion gases and conducting it most efficiently for absorption to the air through the walls of the conduit. By employing a combination of radiation inserts to receive the heat and by then conducting such heat externally of the conduit for absorption by convection, a very etficient heat exchange medium is obtained between the hot flue gases and the incoming air. The air within header chamber 62 is prevented from leaking into chamber 26, not only between the gasket 32 but also by fitting the bottommost convection sleeve within a recess 66 which can be sealed inany suitable manner. The seal can be varied by changing the depth of the seat, or in other words, by changing the depth of lap between the recess 66 and the sleeve.

The weight of the stack of convection sleeves and of bottom header wall 39 are supported through piers 34 which in turn rest on head blocks 20 forming another wall of the air header 62, and the chamber 5% is in turn defined by the bottom terminal head blocks 20 which are carried by the pedestal 70 which rests on foundation 72. As previously explained, the waste gas chamber 50 connects with a stack (not shown) through outlet 52.

In operation, the chamber 26 is operated under several inches of water column pressure, some of this pressure being used advantageously as kinetic energy for the muchimproved convection heat transfer in the narrow confines of the annular passage 60. Since the only function of the convection sleeves is to confine and guide the air, they need not be of the same quality of material as the conduits 36 since their conductivity is of little consequence. Also, no provision is needed for sealing the complementary joints of the convection sleeves since their only purpose is to guide the passage of air and all that is required is a smooth surface since leakage of the points is minimal and is not of critical importance.

The convection sleeves do, however, serve an important secondary function in that they absorb radiant energy from the conduit 36 and provide a large additional amount of convection heating surface for the air as it moves longitudinally and exits ultimately into chamber 26. It is generally provided that the tubular member does not extend within its companion head block by an amount substantially greater than the wall thickness of the tubular member. In this way, tube breakage from the so-called thermal fly-wheel effect is circumvented.

When the tubes extend into the wall blocks by an appreciable amount and the unit is heated up, the relatively small mass of the tube within the block assumes the temperature of the block or the wall mass which is slow to come up to heat. Conversely, that portion of the tube outside the wall will heat up rapidly. When the unit is allowed to cool down, the reverse condition of heat differentials takes place. A sharp line of thermal difference at the wall line produces excessive strains in the tube walls leading to early thermal fractures. In the present invention, not only is there relative expansion and contraction between the tubes and head blocks but because of the method of joining, said relative movement is nonproductive of strains and leakages that give rise to early deterioration of tubes so characteristic of refractory material recuperators or heat exchangers.

The height of the conduits 36 and the height of the stack of convection sleeves 54 determine to a large extent the magnitude or degree of the heat picked up by the air, and the efficiency of the heat pickup is determined by the size of the annuli formed by the conduit and sleeves and the mass velocity of the air through the annuli. These factors in relation to the temperatures of the confining walls determine the total of the heat picked up. Through the proper selection and control of these factors, it is possible to obtain optimum heat exchange and keep the size of the units at near minimums.

The previously described routing of the gas and the air in the counterflow arrangement will attain the highest preheats of any of the possible arrangements. It can do this most efiiciently, but also as pointed out before, at lower preheat goals when the preheat is not to exceed about /3 that of the incoming gas temperature, the use of the concurrent flow arrangement following the same general design can be used with almost equal facility.

Referring now to the concurrent flow which is shown in FIGURE 4, the concurrent flow of hot gases and air will next be described. In this arrangement, the air flow from inlet 22 upwardly through annular chamber and into chamber 26, then outwardly through opening 24 is the same. But the heated flue gases reverse in flow, starting from 52 and traversing upwardly through the conduits 36 and enter chamber 14 where they are collected and continuing to travel the direction of the Wavy-line arrows are connected through 12 to the stack Where they are vented to atmosphere. The sealed relationship of the ends of the conduits instead of being obtained by the cumulative weight of a plurality of counterweight blocks 18 is obtained instead by means of springs 90 which are caged within housings 92, and, acting through pedestals 94 bear against the top terminal head blocks 96 defining the upper head wall 93 separating chamber 26 and chamber 14. The heat exchanger or recuperator is in all other respects the same as the previous invention and operates in substantially the same manner with all of the attendant advantages.

In each of the described embodiments, there is no restriction on the height the gas chambers may be and the required gas flow areas may be easily obtained. A covering structure may be of the sprung arch type or of the flat, suspended roof type, either of which is easier construction than the cast type.

Although the present invention has been illustrated in connection with selected example embodiments of the invention, it will be understood that these are illustrative and are in no sense restrictive of the invention. It is reasonably to be presumed that those skilled in the art can make numerous revisions and adaptations of the invention in order to meet specific design requirements, and it is intended that such revisions and adaptations as incorporate the herein disclosed principles will be included within the scope of the following claims as equivalents of the invention.

I claim:

1. A heat exchanger comprising an inlet chamber having a plurality of individually movable blocks forming a floatable wall defining said chamber and wherein said blocks are each adapted to move relatively to each other for providing differential expansion therebetween, an outlet chamber also including a plurality of blocks forming a floatable wall defining a portion thereof and wherein said blocks are each adapted to move one relatively to the other, a plurality of conduit means having bearing connections with respective aligned pairs of said blocks to conduct a flow of gas between said inlet and outlet chambers, a second conduit surrounding each of said first conduits and spaced slightly therefrom to provide an annular cross section passage extending substantially the length of said first conduit to channel a flow of gases therethrough and thereby effect a heat exchange between the fiow of gases in said first conduit and annular passage, means for conducting a flow of gas to said inlet and outlet chambers to collect the flow of gas after its passage through said conduit means.

2. A heat exchanger comprising inlet and oulet chambers, each having a wall provided at least in part by individual ceramic blocks separated one from the other by expansion joints, means for sealing said joints and permitting relative movement therebetween, a plurality of conduits having gas-tight connections with respective pairs of said blocks in the respective inlet and outlet chambers to conduct a flow of gas between said inlet and outlet chambers, a plurality of second conduits forming stacks, one stack surrounding each of said first conduits and de fining an annular passageway surrounding each first conduit to conduct a flow of gas which is at a temperature differential with the flow of gas in said first conduit and thereby effects an exchange of heat therebetween, a chamber means for conducting a flow of gas to said annular passageways, and chamber means for collecting said flow of gases after their movement through said annular passageways.

3. A heat exchanger comprising separated inlet and outlet gas chambers which are separated one from the other and include at least one floatable wall defined by a plurality of individually floatable ceramic blocks having expansion joints means therebetween which provide relative thermal expansion movement of each block independently of the other and while the respective blocks are held in operative position, a middle chamber disposed between said inlet and outlet chambers and defined in part by the walls provided by said individually floatable ceramic blocks, conduit means extending between said inlet and outlet chambers to conduct a hot flow of gas therebetween and through said middle chamber, a hearing connection between said conduits at the opposite ends thereof with said respective blocks associated with said inlet and outlet chambers respectively and having gastight connections therewith whereby gases moving through said conduits are restricted from leakage into said middle chamber, a sleeve surrounding each of said first conduits to provide an annular cross section gas flow passage for gas which is at a temperature differential with the gas flow between said inlet and outlet chambers to promote a mean tempearture therebetween, and means for collect ing the gases after their passage through said annular passages and have effected a heat exchange with said hot flow of gases.

4. A heat exchanger comprising an inlet chamber for receiving an inflow of hot gas, an outlet chamber spaced from said first chamber and having a plurality of conduits for conducting gas flow from said inlet to said out let chamber, a middle chamber through which said conduits extend and which is fluid-tightly sealed from said inlet and outlet chambers, a plurality of sleeves surrounding said conduits are provided in stacked sections surrounding each of said first conduits to provide an annular cross section passageway extending longitudinally of said conduit and opening into said middle chamber, means for conducting a second flow of gas to the annular passageways for flow therethrough, and means for conducting the flow of gases out of said middle chamber after their heat exchange with the first flow of gases.

5. A heat exchanger comprising a chamber having a plurality of ceramic blocks each having expansion joints means therebetween providing relative expansion and contraction movements induced by differential heating thereof and defining opposite floatable Walls, a plurality of conduits having gas-tightly sealed thrust connections at the opposite ends thereof with said ceramic blocks to conduct a flow of gases through said chamber, means for yieldably urging said conduits into sealing engagement at the opposite ends thereof with their respective ceramic blocks whereby each conduit is float-ably associated with said blocks and each conduit is independently movable during thermal expansion or contraction of its respective head blocks, a plurality of ceramic members each having an opening therein and surrounding a respective one of said conduits and proportioned to provide a spacing forming an annular cross section passage of predetermined length surrounding each of said first conduits, means for conducting a second flow of gases to said annular passages for movement therethrough effecting a heat exchange with the gases flowing in said first conduits and thereafter dis charging into said chamber.

6. A heat exchanger for heating the supply gases communicated to a furnace or the like by effecting a heat exchange With flue gases which are discharged from said furnace or the like comprising a chamber defined at opposite wall portions by a plurality of refractory ceramic head blocks each having an expansion joint means separating it from its adjacent head blocks to provide relative expansion and contraction movement therebetween, a plurality of heat resistant high thermal conductivity and low permeability ceramic conduits having floating gas-tight thrust connections means with aligned pairs of said blocks to conduct a flow of hot gas from said furnace or the like through said chamber, a plurality of ceramic block members having an opening proportioned to fit over said conduits and formed in stacks to define a jacket having an annular cross section passageway extending substantially the length of said first conduits, means for conducting a flow of air through said annular passageways for preheating with the countercurrent flow of hot flue gases in said first conduits and discharging into said cham- 9': ber, and means for conducting the preheated air inlet flow discharging into said chamber to the furnace or the like for combustion purposes.

7. A heat exchanger adapted for operation with a countercurrent flow of flue gases and air comprising a chamber defined by a plurality of individually movable head blocks defining upper and lower fioatable wall structures, said plurality of head blocks each having a channel of compressible heat-resistant ceramic material providing relative expansion and contraction of each head block relative to its contiguous head block whereby expansion forces are noncumulative within said upper and lower floatable wall structures respectively, said upper and lower head blocks being adapted for maintaining gaseous pressures within said chamber in the order of 12 inches we and temperatures in the order of 2500 F.

8. A heat exchanger adapted for operation with a countercurrent flow of flue gases and air comprising a gas chamber defined a plurality of individually movable head blocks providing by upper and lower floatable wall structures, each of said head blocks having a rabbeting of compressible heat-resistant ceramic material providing relative expansion and contraction of each head block relative to its contiguous head block whereby expansion forces are noncumulative within said upper and lower fioatable wall structures respectively, said upper and lower head blocks being adapted for maintaining gaseous pressures within said chamber in the order of 12 inches we. and temperatures in the order of 2500 F., refractory heat-resistant conduit means for conducting a flow of hot gases through said chamber and comprised of heat conductive wall construction whereby the inner and outer walls of said conduit means are substantially uniformly heated, and a plurality of refractory annular sleeves sur rounding said conduit means and defining an annular passage providing counter-current gaseous flow which moves oppositely to the fiow within said conduit means to effect a heat exchange therewith and thereafter enter said chamber.

9. A heat exchanger adapted for operation with a countercurrent flow of flue gases and air comprising a gas chamber defined by a plurality of head blocks providing upper and lower floatable wall structures each of said plurality of head blocks having a rabbeting of compressible heat-resistant ceramic material roviding relative expansion and contraction of each head block relative to its contiguous head block whereby expansion forces are noncumulative within said upper and lower wall structures respectively, said upper and lower head blocks being adapted for maintaining gaseous pressures within said chamber in the order of 12 inches W.c. and temperatures in the order of 2500 F refractory heat-resistant conduit means for conducting a flow of hot gases through said chamber and comprised of a heat conductive wall construction whereby the inner and outer walls of said conduit means are substantially uniformly heated, and a plurality of refractory annular sleeves surrounding said conduit means and defining an annular passage providing countercurrent gaseous flow which moves oppositely to the flow within said conduit means to effect a heat exchange therewith and thereafter enter within said chamber, said sleeves being formed in a vertical stack to define an annular channel of predetermined height whereby the air being heated is exposed for a predetermined period to the heat contained within said conduit means, said sleeves having inner surfaces opposed to the outer surfaces of said conduit means to provide additional heat exchanging areas for said gas.

10. A heat exchanger construction comprising a chamber having a plurality of refractory head blocks defining two floatable walls and which form at least a portion of said chamber, a compressible heat-resistant ceramic material forming a gasket protection about said head blocks to provide relative expansion therebetween while maintaining a gas-tight connection across said floatable walls, conduit means extending through said chamber and having inlet and outlet connections with said head blocks whereby a stream of heated gas is caused to flow through said conduit means, and a plurality of annular members surrounding said conduit means to provide an annular passageway wherein gas is flowed counter-currently to the gas flow within said conduit means and thereby effecting a heat interchange between the gaseous media.

11. A heat exchanger construction comprising a chamber having a plurality of refractory head blocks defining Walls and forming at least a portion of said chamber, a compressible heat-resistant ceramic material forming a gasket protection about said head blocks to provide relative expansion therebetween while maintaining a gastight connection across said walls, conduit means extending through said chamber and having inlet and outlet connections with said head blocks whereby a stream of heated gas is caused to flow through said conduit means and past said walls, a plurality of annular members surrounding said conduit means to provide an annular passageway wherein gas is flowed countercurrently to the gas flow within said conduit means and thereby effecting a heat interchange between the gaseous media, and means for effecting said countercurrent gaseous flow through said conduit means at a pressure of as high as 12 inches we. and gas temperatures as high as 2500 F.

12. The structure in accordance with claim 11 including a plurality of head blocks forming a stack at the upper Wall providing a biasing efiect whereby said conduit means are held sealingly in engagement at the opposite ends thereof with said walls.

13. A heat exchanger comprising means'defining a channel for air flow, conduit means for channeling a high temperature gas flow and having a heat conductive wall, said two flows effecting a heat exchange therebetween, two support walls comprised of individually floatable head blocks and vertically supporting said channel defining means and conduit means respectively and each including tapered resilient sealing members which provide for relative expansion and contraction movements of said channel and conduit means while maintaining a sealed relation therebetween.

14. A heat exchanger comprising first conduit means having a core of heat absorptive and heat radiant material and providing relatively unimpeded flow of hot gas longitudinally therein, second conduit means surrounding said first conduit to channel a flow of lower temperature gas in heat-exchanging relation with the hot gas flow, and spacer means disposed within the annular space between said first and second conduit means for separating said first and second conduit means to define an annular cross section channel for said flow of lower temperature gas without impeding the free fiow of gases 1ongitudinally within said annular cross section channel.

15. A heat exchanger in accordance with claim 14 wherein said hot gas and lower temperature gas are oppositely flowing in countercurrent heat exchange relation.

16. The heat exchanger in accordance with claim 14 wherein said hot gas and lower temperature gas are flowing in the same direction in concur-rent heat exchange relation.

17. The heat exchanger in accordance with claim 14 including a header chamber having one wall in vertical support relation with said first conduit means and another wall in vertical support relation with a second conduit means, and means for sealing said conduits against gaseous communication and providing for relatively free longitudinal and lateral floating movements, said header chamber being in open communication with one of said conduit means.

18. The heat exchanger in accordance with claim 14 including means providing vertical support for said cores within the surrounding first conduit means but permitting relatively free passage of hot gas flow.

19. The heat exchanger in accordance with claim 14 including a plurality of distinct chambers, the ends of said conduit opening respectively into a single one of said chambers, a plurality of individually movable head blocks defining a floating wall separating adjoining ones of said chambers, and sealing means providing relative expansion and contraction of said walls while maintaining sealed relation with its respective conduit ends.

20. A sealing and expansion floating joint for a heat exchanger comprising, in combination, a first head block and a relatively movable second block which is free to move relatively to the first head block, said first head block having a tapered recess disposed along one end, said second head block having a tapered recess disposed along one end, said first and second head blocks disposed adjacent each other so that the tapered recesses form a channel portion which is narrow at one end and broad at the other end, a ceramic gasket material disposed in said channel whereby when the blocks are expanded, the gasket material in the narrow portion of the channel is compacted and seals tightly and the gasket material in the broad portion of the channel being less compactable will have a tendency to retain its natural resiliency.

21. A heat exchanger comprising a plurality of heat conductive head blocks which are relatively movable with respect to each other to form a floatable wall defining an internal passage means and an external passage means, one of said passage means effecting transfer of heat primarily by radiation mechanism and including a plurality of heat absorptive Walls adapted to receive by a high surface area-volume ratio a quantity of heat from a current of hot gases flowing therein, and means for channeling a relatively high velocity of gas through a relatively narrow passageway effecting a substantial velocity of gas flow and having heated surface areas defining the pathway of such flow.

22. In a heat exchange apparatus effecting transfer of heat between two gaseous media by radiation and convection heat transfer mechanism, a first heat exchange chamber including within the interior of such chamber a plurality of radiation inserts defining a high surface areavolume chamber for absorbing heat and emitting such heat by radiation to the heat-conductive walls surrounding said chamber but without substantially obstructing the flow of gases longitudinally within said first heating exchange chamber, and a second chamber defined in part by the heat-conductive wall of said first chamber and including a second heated wall which channels a relatively high velocity gaseous flow which receives heat primarily by convection medium by its passage through a relatively narrow spacing between the heated walls defining its pathway of movement, and means defining the spacing provided between said first and second chambers.

23. A floating joint for a heat exchanger comprising, in combination, a first head block and a second block relatively movable to said first head block to provide free floating movement therebetween, said first head block having a tapered recess disposed along one end, said second head block having a tapered recess disposed along one end, said first and second head blocks disposed adjacent each other so that the tapered recesses form a channel portion which is narrow at one end and broad at the other end, a ceramic gasket material disposed in said channel whereby when the blocks are expanded the gasket material in the narrow portion of the channel is compacted and seals tightly and the gasket material in the broad portion of the channel being less compacted will have a tendency to retain its natural resiliency.

References Cited by the Examiner UNITED STATES PATENTS 550,804 12/1895 Saxton 126-109 X 1,481,348 1/1924 Chapman 263-20 1,599,613 9/1932 Fahrenwald 263-20 1,877,599 9/1932 Schwalbe 263-20 1,925,711 9/1933 Batchell 263-20 2,035,309 3/1936 Fitch 263-20 X 2,092,402 9/1937 Morton et al. 263-20 2,262,530 11/ 1941 Hamlink 126-91 2,598,474 5/1952 Weaver 126-91 2,632,503 3/1953 Bailey 1 26-91 2,917,285 12/1959 Schack 263-20 X 3,030,092 4/1962 Hildenbrand 126-91 3,121,559 2/1964 Tippman 263-20 WILLIAM F. ODEA, Acting Primary Examiner. JOHN J. CAMBY, Examiner. 

14. A HEAT EXCHANGER COMPRISING FIRST CONDUIT MEANS HAVING A CORE OF HEAT ABSORPTIVE AND HEAT RADIANT MATERIAL AND PROVIDING RELATIVELY UNIMPEDED FLOW OF HOT GAS LONGITUDINALLY THEREIN, SECOND CONDUIT MEANS SURROUNDING SAID FIRST CONDUIT TO CHANNEL A FLOW OF LOWER TEMPERATURE GAS IN HEAT-EXCHANGING RELATION WITH THE HOT GAS FLOW, AND SPACER MEANS DISPOSED WITHIN THE ANNULAR SPACE BETWEEN SAID FIRST AND SECOND CONDUIT MEANS FOR SEPARATING SAID FIRST AND SECOND CONDUIT MEANS TO DEFINE AT ANNULAR CROSS SECTIONAL CHANNEL FOR SAID FLOW OF LOWER TEMPERATURE GAS WITHOUT IMPEDING THE FREE FLOW OF GASES LONGITUDINALLY WITHIN SAID ANNULAR CROSS SECTION CHANNEL. 